All the planets except for Mercury and Venus have a
system of moons. Think about that. Nine planets circle the
Sun, most of those planets have moons which circle them.
That is a lot of worlds. There are over 90 known worlds in the
Solar System.

The only difference between a planet and a moon is
that a planet circles the Sun while a moon circles a
planet. Everything else about them is similar.
Seven of the moons in our Solar System are even bigger than some of the
planets. There are moons with atmospheres, volcanoes and even oceans.